add configuration manager

src/CMakeLists.txt

src/caosdb/configuration.cpp

src/caosdb/connection.cpp

src/ccaosdb.cpp

src/cxxcaosdbcli.cpp

test/CMakeLists.txt

test/caosdb_test_utility.h.in

test/test_ccaosdb.cpp

test/test_configuration.cpp

test/test_connection.cpp

.../test_data/test_broken_caosdb_client_no_connections1.json

.../test_data/test_broken_caosdb_client_no_connections2.json

.../test_data/test_broken_caosdb_client_no_connections3.json

test/test_data/test_caosdb_client.json